Electric discharge tubes



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July 17, 1962 w. J. ol-n. 3,045,138

ELECTRIC DISCHARGE ,TUBES Filed Jan. 10, 1958 Inventor W. l'PoH AttorneyUnited States Patent 3,045,138 ELECTRIC DISCHARGE TUBES Walter JohnPohl, London, England, assignor to International Standard ElectricCorporation, New York, N.Y., a corporation of Delaware Filed Jan. 10,1958, Ser. No. 708,134 Claims priority, application Great Britain Feb.13, 1957 3 Claims. (Cl. 313-21) The present invention relates toelectron discharge tubes cooled by the latent heat of evaporation of acooling liquid.

It has previously been proposed to cool the anodes of high powerthermionic valves having external anodes by supporting the valve withthe anode immersed in cooling liquid contained within a boiler, thetemperature of the coolant liquid being allowed to rise to boiling pointso that the dissipation of heat is largely accomplished by utilising thelatent heat of evaporation of the liquid. In general it is known that itis not satisfactory merely to place the smooth anode of the conventionalwater-cooled valve in the cooling liquid, but steps have to be taken toensure that bubbles of gas do not collect on the anode surface, therebygiving rise to hot spots, while it is also desirable to provide a largesurface in contact with the coolant. It has therefore been proposed toutilise an anode structure in which the surface is covered by a numberof protuberances which serve not only to increase the eifective surfacearea but also to mitigate against the likelihood of bubbles of vapourbecoming lodged in contact with the anode.

We have found that satisfactory latent heat cooling can be achieved withanode surfaces of comparatively simple configuration, and, in accordancewith the present invention, we provide an electron discharge tube havingan external anode whose external surface carries grooves which extendsubstantially continuously around the circumference of the anode.Although the groove shaping does not appear to be unduly critical itmust, of course, be such as not to encourage the trapping of vapourbubbles; preferably the groove shape is of semi-V formation with onebounding wall substantially horizontal when the discharge tube is in itsoperating position and the other groove bounding wall inclined at anacute angle to and above the first mentioned groove bounding wall. Thegrooves may be provided very simply by turning a screw thread in theanode wall or, if desired, a comparatively thin wall sleeve in whichsuch grooves are turned can be fitted over and secured to the smoothanode of a conventional water-cooled valve.

An embodiment of the invention will be described with reference to theaccompanying drawings in which:

FIG. 1 is an outline drawing of an electron discharge tube according tothe invention; 7

FIG. 2 shows a longitudinal cross-section through a sleeve to be fittedto a standard smooth-walled anode; and

FIG. 3 is an enlarged view of part of the sleeve wall.

In the embodiment of FIG. 1 the tube 1 comprises an external anode 2joined by means of glass envelope portion 3 to a grid ring 4 whichsupports a control grid coaxially inside the anode 2. Another length ofglass envelope portion '5 separates the grid ring 4 from'a filament ring6 which similarly supports one end of a directly heated cathode within,the grid and anode electrodes. The other end of the cathode is takenout to a further ring 7 separated by a glass collar 8 from the ring 6.The

3,045,138 Patented July 17, 1962 'ice discharge tube is terminated atthis end by a cap 9 secured a flange 10 has to be spaced somewhat awayfrom the glassto-metal seal, as is indicated in the drawing.

Between the flange 10 and the lower end of the anode 2 the anode surface12 is grooved. The form of the grooves is similar to that shown in FIG.3, in which each lower groove-bounding-wall 13 is substantiallyhorizontal and each upper groove-bounding-wall 14 is inclined at anacute angle to the adjacent bounding wall 13 below it. Furthermore, inits preferred form each slant groovebounding-wall surface intersects theadjacent horizontal groove-bounding wall surface above it so that thecrosssection as shown in FIG. 3 has a saw-tooth boundary.

The grooves in the anode surface can conveniently be formed by turning ascrew thread on a lathe. Alternatively, if it is desired to modify astandard water-cooled valve for latent heat cooling a sleeve such asshown in FIG. 2 can be fitted over the anode.

The sleeve of FIG. 2 comprises a thin walled copper tube inwhich groovesare cut. In a typical embodiment the sleeve wall thickness was 0.150",the depth of the grooves.(surface 13, FIG. 3) was 0.100 and the spacingbetween adjacent grooves Was 0.143". A discharge tube provided with suchgrooves covering sq. cms. of cylindrical anode surface was shown to beable to dissipate comfortably 17 kilowatts, Whereas a similar tubehaving the normal smooth anode surface was only able to dissipate justover half this power.

While the principles of the invention have been described above inconnection with specific embodiments, and particular modificationsthereof, it is to be clearly understood that this description is madeonly by way of example and not as a limitation on the scope of theinvention.

What I claim is:

1. An anode structure for an electron discharge tube adapted to beimmersed in a liquid coolant and to be cooled by the latent heat ofevaporation thereof, said structure comprising a cylindrically shapedanode having a series of annular grooves extending around the outsidecircumference of said anode, each of said grooves being defined by alower surface which is substantially normal to the vertical axis of thetube when in its operating position, and an upper surface inclined at anacute angle to said lower surface.

2. An anode structure according to claim 1 in which the distance betweenadjacent horizontal grooves are between one and one and one-half timesthe radial depth of said grooves.

3. An' anode structure according to claim 1, wherein said series ofannular grooves are interconnected to form a substantially continuousscrew thread.

References Cited in the file of this patent UNITED STATES PATENTSManfredi Nov. 13, 1956 I

